INFO2010 - L7 Architecture and Infrastructure

Question 1

Architecture

Answer 1

High level map of the information requirements in organisation

Question 2

Infrastructure

Answer 2

• physical facilities

- services and management that supports all computer resources within an organisation

Question 3

Advantages of explicitly designing and documenting a software architecture
Bass et al (2003)

Answer 3

1. Stakeholder communication - use as focus for discussion by a range of different stakeholders
2. System analysis - making sys arch explicit early in sys dev; architectural design decisions have a profound effect on whether the system can meet critical requirements such as performance, reliability and maintainability
3. Large scale reuse - arch is a compact, manageable description of how a sys is organised and how the the components interoperate; may be reusable across many systems with similar reqs

Question 4

Architectural design stage

Hofmeister et al (2000)

Answer 4

-forces sw designers to consider key design aspects early in the process - arch can serve as a design plan that is used to negotiate system requirements and as a means of structuring discussions with clients, developers and managers. Also essential tool for complexity management. It hides details and allows designers to focus on the key system abstractions

Question 5

Factors affected by sys architecture

Bosch, 2000

Answer 5

1. Performance - if critical; arch design to localise critical ops in a small number of subsystems with little comms btwn them
2. Security - if critical; layered structure design to protect most critical assets in innermost layers with high security
3. Safety - if critical, design to contain all safety related ops in singe sub system or small no of em
4. Availability - if critical design to include redundant components so it is poss to replace and update em without stopping the sys.
5. Maintainability - if critical - design fine grain, self containers components that can be readily changed. Producers of data should be separated from consumers and shared data structures avoided.

Question 6

Probs with Bosch factors

Answer 6

Large grain components improves performance but reduces maintainability
Redundant data improves availability but makes security more difficult
Localising safety features means more comms so degraded performance

Question 7

Architectural design decisions

Answer 7

• is there a generic application arch that can be used?
• how will the system be distributed?
• what architectural styles are appropriate?
• what approach to structure the system?
• how will the system be decomposed into modules?
• what control strategy will be used?
• how will the arch design be evaluated?
• how should the architecture be documented?

Question 8

System organisation

Answer 8

Reflects basic strategy used to structure a system
3 organisational styles:
- shared data repository style
- shared services and servers style 
- abstract machine or layered style

Question 9

Shared data repository style

Answer 9

Sub systems exchange data;

• central database accessed by all subsystems (for large amounts of data)
• sub system centric dbs pass data to other subsystems

Question 10

CASE tools

Answer 10

Project repository in the centre;
sub-systems;
Design Editor
Design Translator
Design Analyser
Report generator
Program editor
Code generator

Question 11

Repository model advantages

Answer 11

• efficient way to share lots of data
• sub-systems not concerned with data management - centralised
• sharing model is published as the repository schema

Question 12

Repository model disadvantages

Answer 12

• sub-systems must agree on a reporitory modes - a compromise
• data evolution is difficult and expensive
• no scope for specific management policies
• difficult to distribute efficiently

Question 13

Client/Server Architecture

Answer 13

CLIENT - computer on a network accesses shared network resources
SERVER - machine provides client with services
- maximise utilisation of computer resources
- sharing expensive hw/sw

Question 14

Client server model

Answer 14

• distributed system model which shows how data and processing is distributed accross a range of components
• set of stnad alone servers which provide specific services such as printing, data management etc
• set of clients which call on these services
• network which allows clients to access servers

Question 15

Example

Answer 15

Film and picture library:
Internet in the middle
On one side clients 1,2,3,4
On the other;
4 libraries and their servers; pic, film, catalogue, webserver

Question 16

Client server advantages

Answer 16

• distribution of data is straightforward
• makes effective use of networked systems
• may require cheaper hardware
• easy to add and upgrade existing servers

Question 17

Client server disadvantages

Answer 17

• no shared data model so sub-systems use different data organisation
• data interchange might be inefficient
• redundant management in each server
• no central register of names and services - may be hard to find out what servers and services are available

Question 18

Enterprise wide client server architecture

Answer 18

Provides total integration of departmental and corporate IS resources
Maximise the value of information by increasing its availability
Can gain a significant competitive advantage
Requires new infrastructure
- considerable impact on people, quality and budget

Question 19

Main Frames

Answer 19

• not dead but a growing biz
• modern, small
• lot of computing power
• little if any down time
• Large Batch Processing
• ATMs, order processing, financial transactions, production and inventory control, payroll

Question 20

Abstract machines (layered) model

Answer 20

• Used to model the interfacing of sub systems
• Organises systems into a set of layers (or abstract machines) each of which provide a set of services
• supports incremental development of sub-systems in different layers
• when an interface layer changes, only the adjacent layer is affected
• it is often artificial to structure systems like this

Question 21

Version Management System

Answer 21

Configuration Management Layer
Object Management Layer
Database System Layer
Operating System Layer

Question 22

Processes of Information management

Answer 22

• Strategic information planning
  
  • IT scanning
  • Participation in org strategy planning
  • Info infrastructures planning
  • Application portfolio planning
• Change management
• Information management operations
• Information management advisory services

Question 23

Distributed System disadvantages

Answer 23

Complexity
Security
Manageability
Unpredictability

Question 24

Distributed system architecture

Answer 24

Client server architecture

Distibuted object architecture
- all objects can share and exchange services

Question 25

Middleware

Answer 25

Manages and supports different components of a distributed system
Sits in the middle of the system
Usually off the shelf
Examples
- transaction processing monitors
- data converters
- communication controllers

Question 26

Distributed Systems characteristics

Answer 26

Resource Sharing
- sharing hw and sw
Openness
- use of hw & sw from diff vendors
Concurrency
Scalability
Fault tolerance